Ultraviolet light damages cellular DNA, primarily by forming dimers between pyrimidine base pairs. UV-induced DNA repair mechanisms are responsible for correcting this DNA damage and preventing cancer formation. The RAD6/RAD18 complex is the central director of these UV-induced DNA repair mechanisms. RAD18 binds damaged DNA, RAD6 binds RAD18, and the complex induces both error-free and error-prone mechanisms of DNA repair. My aim is to determine the structure of the RAD6/RAD18 heterodimeric complex using X-ray crystallographic methods. [unreadable] [unreadable]